Knuckles is the last echidna left. his duty is to gaurd the master emerald. he lives on Angel Island. Knuckles knows little of his past. Knuckles was tricked by Eggman in the past, thinking that Sonic was trying to steal the Master Emerald(Sonic & Knuckles). Eggman shown who was the real evil in this by stealing it himself. Eggman tricks Knuckles again, making him think Sonic was trying to find the pieces of the Master Emerald for himself(Sonic Adventure). Knuckles finds out later that Sonic had no intentions of doing that, & found out that Eggman was bringing a monster from Knuckles' past, Chaos. Chaos whiped out the entire echidna race. Knuckles now gaurds the Master Emerald from any evil that may want to take it's power.